Nonlinear plasmonic metasurfaces, as a subset of metamaterials, allow for active functionality not found in natural optical materials; including switching, wavelength conversion, routing, adaptive focusing. Metasurfaces in particular are compact, cascadable and easy to fabricate with established planar technologies, and therefore deserve particular attention.
Here we focus on nonlinear plasmonic metasurfaces, where the nonlinear response of the metal is considered in nanostructured plasmonic metasurfaces. Past works have demonstrated that the Lorentz contribution to nonlinear plasmonic metasurfaces is typically negligible. In this work, we discuss the physical reasons why this is true and show experimental results of designs where the Lorentz contribution is maximized, with some surprising results.
Finally, the prospects of these demonstrations for future metasurface applications, including high efficiency wavelength conversion, are discussed.
Double nanohole optical tweezers allow for trapping of nanoparticles down to single digit nanometer range, including individual proteins, viruses, DNA fragments and quantum dots. Here we demonstrate dual magnetic force / optical force analysis for the characterization of magnetic nanoparticles. From this single platform we can isolate individual nanoparticles and determine their size, permeability, remanence and permittivity. This is of interest for characterizing magnetic nanoparticles in mixtures, isolating ones of desired characteristics and pick-and-place assembly of magnetic nanoparticles in nanoscale magnetic devices.
The magnetic nanoparticle is characterized by analysis of the optical transmission through a double-nanohole aperture with an applied magnetic gradient force. The optical transmission step at trapping, autocorrelation of transmission intensity, distribution of transmission values and variations with applied magnetic field amplitude provide information of individual magnetic nanoparticles that allows for determining their individual material characteristics. The values obtained agree well with past published values for iron oxide, and the size distribution over repeated measurements matches well with scanning electron microscope characterization (and manufacturer specifications).